Relation Liftings on Preorders and Posets

The category Rel(Set) of sets and relations can be described as a category of spans and as the Kleisli category for the powerset monad. A set-functor can be lifted to a functor on Rel(Set) iff it preserves weak pullbacks. We show that these results extend to the enriched setting, if we replace sets by posets or preorders. Preservation of weak pullbacks becomes preservation of exact lax squares. As an application we present Moss's coalgebraic over posets

Knowledge Propagation in Contextualized Knowledge Repositories: an Experimental Evaluation

As the interest in the representation of context dependent knowledge in the Semantic Web has been recognized, a number of logic based solutions have been proposed in this regard. In our recent works, in response to this need, we presented the description logic-based Contextualized Knowledge Repository (CKR) framework. CKR is not only a theoretical framework, but it has been effectively implemented over state-of-the-art tools for the management of Semantic Web data: inference inside and across contexts has been realized in the form of forward SPARQL-based rules over different RDF named graphs. In this paper we present the first evaluation results for such CKR implementation. In particular, in first experiment we study its scalability with respect to different reasoning regimes. In a second experiment we analyze the effects of knowledge propagation on the computation of inferences.Comment: ARCOE-Logic 2014 Workshop Notes, pp. 13-2

Bifinite Chu Spaces

This paper studies colimits of sequences of finite Chu spaces and their ramifications. Besides generic Chu spaces, we consider extensional and biextensional variants. In the corresponding categories we first characterize the monics and then the existence (or the lack thereof) of the desired colimits. In each case, we provide a characterization of the finite objects in terms of monomorphisms/injections. Bifinite Chu spaces are then expressed with respect to the monics of generic Chu spaces, and universal, homogeneous Chu spaces are shown to exist in this category. Unanticipated results driving this development include the fact that while for generic Chu spaces monics consist of an injective first and a surjective second component, in the extensional and biextensional cases the surjectivity requirement can be dropped. Furthermore, the desired colimits are only guaranteed to exist in the extensional case. Finally, not all finite Chu spaces (considered set-theoretically) are finite objects in their categories. This study opens up opportunities for further investigations into recursively defined Chu spaces, as well as constructive models of linear logic

A Datalog Hammer for Supervisor Verification Conditions Modulo Simple Linear Arithmetic

The Bernays-Sch\"onfinkel first-order logic fragment over simple linear real arithmetic constraints BS(SLR) is known to be decidable. We prove that BS(SLR) clause sets with both universally and existentially quantified verification conditions (conjectures) can be translated into BS(SLR) clause sets over a finite set of first-order constants. For the Horn case, we provide a Datalog hammer preserving validity and satisfiability. A toolchain from the BS(LRA) prover SPASS-SPL to the Datalog reasoner VLog establishes an effective way of deciding verification conditions in the Horn fragment. This is exemplified by the verification of supervisor code for a lane change assistant in a car and of an electronic control unit for a supercharged combustion engine

Approximate OWL-Reasoning with Screech

Applications of expressive ontology reasoning for the Semantic Web require scalable algorithms for deducing implicit knowledge from explicitly given knowledge bases. Besides the development of more effi- cient such algorithms, awareness is rising that approximate reasoning solutions will be helpful and needed for certain application domains. In this paper, we present a comprehensive overview of the Screech approach to approximate reasoning with OWL ontologies, which is based on the KAON2 algorithms, facilitating a compilation of OWL DL TBoxes into Datalog, which is tractable in terms of data complexity. We present three different instantiations of the Screech approach, and report on experiments which show that a significant gain in efficiency can be achieved

QuiKey – An Efficient Semantic Command Line

Abstract. QuiKey is an interaction approach that offers interactive fine grained access to structured information sources in a light weight user interface. It is designed to be highly interaction efficient for searching, browsing and authoring semantic knowledge bases as well as incremen-tally constructing complex queries. Empirical evaluation using a compar-ative GOMS Analysis and a user study confirm interaction efficiency.

A Sorted Datalog Hammer for Supervisor Verification Conditions Modulo Simple Linear Arithmetic

International audienceAbstract In a previous paper, we have shown that clause sets belonging to the Horn Bernays-Schönfinkel fragment over simple linear real arithmetic (HBS(SLR)) can be translated into HBS clause sets over a finite set of first-order constants. The translation preserves validity and satisfiability and it is still applicable if we extend our input with positive universally or existentially quantified verification conditions (conjectures). We call this translation a Datalog hammer. The combination of its implementation in SPASS-SPL with the Datalog reasoner VLog establishes an effective way of deciding verification conditions in the Horn fragment. We verify supervisor code for two examples: a lane change assistant in a car and an electronic control unit of a supercharged combustion engine. In this paper, we improve our Datalog hammer in several ways: we generalize it to mixed real-integer arithmetic and finite first-order sorts; we extend the class of acceptable inequalities beyond variable bounds and positively grounded inequalities; and we significantly reduce the size of the hammer output by a soft typing discipline. We call the result the sorted Datalog hammer. It not only allows us to handle more complex supervisor code and to model already considered supervisor code more concisely, but it also improves our performance on real world benchmark examples. Finally, we replace the before file-based interface between SPASS-SPL and VLog by a close coupling resulting in a single executable binary

A Sorted Datalog Hammer for Supervisor Verification Conditions Modulo Simple Linear Arithmetic

In a previous paper, we have shown that clause sets belonging to the HornBernays-Sch\"onfinkel fragment over simple linear real arithmetic (HBS(SLR))can be translated into HBS clause sets over a finite set of first-orderconstants. The translation preserves validity and satisfiability and it isstill applicable if we extend our input with positive universally orexistentially quantified verification conditions (conjectures). We call thistranslation a Datalog hammer. The combination of its implementation inSPASS-SPL with the Datalog reasoner VLog establishes an effective way ofdeciding verification conditions in the Horn fragment. We verify supervisorcode for two examples: a lane change assistant in a car and an electroniccontrol unit of a supercharged combustion engine. In this paper, we improve ourDatalog hammer in several ways: we generalize it to mixed real-integerarithmetic and finite first-order sorts; we extend the class of acceptableinequalities beyond variable bounds and positively grounded inequalities; andwe significantly reduce the size of the hammer output by a soft typingdiscipline. We call the result the sorted Datalog hammer. It not only allows usto handle more complex supervisor code and to model already consideredsupervisor code more concisely, but it also improves our performance on realworld benchmark examples. Finally, we replace the before file-based interfacebetween SPASS-SPL and VLog by a close coupling resulting in a single executablebinary.<br

DSMW: Distributed Semantic MediaWiki

International audienceDSMW is an extension to Semantic Mediawiki (SMW), it allows to create a network of SMW servers that share common semantic wiki pages. DSMW users can create communication channels between servers and use a publish-subscribe approach to manage the change propagation. DSMW synchronizes concurrent updates of shared semantic pages to ensure their consistency. It oers new collaboration modes to semantic wiki users and supports data ow-oriented processes.DSMW est une extension de Semantic MediaWiki (SMW) qui permet de créer un réseau de serveurs SMW partageant des pages communes. Les utilisateurs créent des canaux de communication entre les serveurs pour propager les changements. Le système synchronise les modifications concurrentes pour garantir leur consistance

The Vienna history Wiki: a collaborative knowledge platform for the city of Vienna

The Vienna City Archive and the Vienna City Library have joined forces with several other institutions in Vienna, Austria to create the "Wien Geschichte Wiki" (Vienna History Wiki), a knowledge platform for the history of Vienna with more than 34,000 articles and 120,000 visits per month. The wiki is powered by Semantic MediaWiki and serves not only as an online encyclopedia, based on a digitized printed publication for everybody to use and contribute to, but also as a central knowledge base for several administrative departments of the city administration. In a peer-review process, wiki edits are checked before they become visible. The paper highlights the unique aspects of the Vienna History Wiki related to content creation, governance structures and technology choices. A usage log analysis and an online survey have been carried out to gain first insights after six months of operation